Rhea in Relief

NASA - Cassini Mission to Saturn patch.

April 21, 2015

Rhea in Relief

Surface features on Rhea - mostly impact craters in this image - are thrown into sharp relief thanks to long shadows. Viewing this terrain near the day/night terminator makes it easier to appreciate just how violent Rhea's geological history has been.

The craters on Rhea (949 miles, or 1,527 kilometers across) are the result of 4.6 billion years of bombardment by small bodies. With very little erosion, the scars and craters remain unless they are overwritten by other, newer impacts.

This view looks toward the anti-Saturn hemisphere of Rhea. North on Rhea is up and rotated 11 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 10, 2015.

The view was acquired at a distance of approximately 47,000 miles (76,000 kilometers) from Rhea. Image scale is 1,500 feet (460 meters) per pixel.

Cassini spacecraft

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org and http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Images, Text, Credits: NASA/JPL-Caltech/Space Science Institute.

Greetings, Orbiter.ch

Ceres' Bright Spots Come Back Into View

NASA - Dawn Mission patch.

April 20, 2015

Image above: This image shows the northern terrain on the sunlit side of dwarf planet Ceres as seen by NASA's Dawn spacecraft on April 14 and 15, 2015. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

The two brightest spots on dwarf planet Ceres, which have fascinated scientists for months, are back in view in the newest images from NASA's Dawn spacecraft. Dawn took these images on April 14 and 15 from a vantage point 14,000 miles (22,000 kilometers) above Ceres’ north pole.

The images show the brightest spot and its companion clearly standing out against their darker surroundings, but their composition and sources are still unknown. Scientists also see other interesting features, including heavy cratering. As Dawn gets closer to Ceres, surface features will continue to emerge at increasingly better resolution.

Dawn has now finished delivering the images that have helped mission planners maneuver the spacecraft to its first science orbit and prepare for subsequent observations. All of the approach operations have executed flawlessly and kept Dawn on course and on schedule. Beginning April 23, Dawn will spend about three weeks in a near-circular orbit around Ceres, taking observations from 8,400 miles (13,500 kilometers) above the surface. On May 9, Dawn will begin to make its way to lower orbits to improve the view and provide higher-resolution observations.

Animation above: his animated sequence of images from NASA's Dawn spacecraft shows northern terrain on the sunlit side of dwarf planet Ceres. Dawn took these images on April 14 and 15 from a vantage point 14,000 miles (22,000 kilometers) above Ceres' northern hemisphere. The spacecraft was settling into its first circular orbit, called RC3 (for "rotation characterization 3"), which it will begin on April 23.

The bright feature called "spot 5" by the Dawn science team -- actually two bright spots close together -- rotates into view at right in the last few frames. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

"The approach imaging campaign has completed successfully by giving us a preliminary, tantalizing view of the world Dawn is about to start exploring in detail. It has allowed us to start asking some new and intriguing questions," said Marc Rayman, Dawn's mission director and chief engineer, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

Dawn spacecraft heading Ceres. Image Credit: NASA

On March 6, Dawn became the first spacecraft to orbit a dwarf planet, and the first to orbit two extraterrestrial targets. Scientists will be comparing Ceres to giant asteroid Vesta, which Dawn studied from 2011 to 2012, in order to gain insights about the formation of our solar system. Both Vesta and Ceres, located in the main asteroid belt between Mars and Jupiter, were on their way to becoming planets before their development was interrupted.

Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK, Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team. For a complete list of acknowledgements, visit http://dawn.jpl.nasa.gov/mission

For more information about Dawn, visit: http://dawn.jpl.nasa.gov

Image (mentioned), Text, Credits: NASA/JPL/Elizabeth Landau.

Greetings, Orbiter.ch

Intense X-rays sculpt Thor’s neon-hued helmet

ESA - XMM-Newton Mission patch.

April 20, 2015

This brightly coloured scene shows a giant cloud of glowing gas and dust known as NGC 2359. This is also dubbed the Thor’s Helmet nebula, due to the arching arms of gas stemming from the central bulge and curving towards the top left and right of the frame, creating a shape reminiscent of the Norse god’s winged helmet.

The neon colours in this image are not just beautiful, they also tell us about the nebula’s composition. The bright blue patches show X-ray emission, spotted by the EPIC cameras on ESA’s XMM-Newton space observatory, while the pale red and green regions trace the glow from ionised hydrogen and oxygen, as seen by the Stars and Shadows Remote Observatory South at the Cerro Tololo Inter-American Observatory.

The intense X-ray emission detected by XMM-Newton is emanating from a star at the centre of the nebula. This star, a Wolf-Rayet star named HD 56925, is old, massive and pushing out incredible amounts of material at a staggering pace: the star loses a mass equivalent to that of the Sun in less than 100 000 years, in the form of a wind moving faster than 1500 km/s.

Having such violent inhabitants has influenced NGC 2359’s messy shape. The nebula consists of a central bubble surrounded by a tangled web of gaseous filaments, thick channels of dark dust and bright outbursts, where material swept up by the stellar wind has collided with the surrounding gas and triggered rippling shock waves throughout the region.

XMM-Newton space observatory

The blue patches in this image highlight the nebula’s hottest regions: the central bubble and a blowout to its lower left. NGC 2359’s gas is thought to reach temperatures ranging from several million up to tens of millions of degrees.  

This image combines X-ray data collected in 2013 by XMM-Newton (blue) with optical observations from Cerro Tololo in Chile (green and red). North is to the left, west is up. It was first published in the XMM-Newton image gallery.

Related link:

XMM-Newton image gallery: http://xmm.esac.esa.int/external/xmm_science/gallery/public/level3.php?id=1195

For more information about XMM-Newton, visit: http://sci.esa.int/xmm-newton/

Images, Text, Credits: ESA/J.A. Toala & M.A. Guerrero (IAA-CSIC), Y.-H. Chu (UIUC/ASIAA), R.A. Gruendl (UIUC), S. Mazlin, J. Harvey, D. Verschatse & R. Gilbert (SSRO-South).

Greetings, Orbiter.ch

Rosetta new image of Comet 67P/Churyumov-Gerasimenko

ESA - Rosetta Mission patch.

April 18, 2015

Single frame NAVCAM image obtained on 15 April, from a distance of 170 km from the centre of Comet 67P/Churyumov-Gerasimenko. At this distance, the resolution is 14.5 m/pixel; the image has been cropped to 11.4 km (the original frame, provided at the end of the post, measures 14.8 km across).

Comet on 15 April 2015 – NavCam

Image above: Cropped and processed single frame NAVCAM image of Comet 67P/C-G taken on 15 April 2015 from a distance of 170 km to the comet centre. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

Image above shows 67P/C-G from an unusual angle, revealing some regions on the comet nucleus that in previously published images were partly cast in shadow.

In this orientation, the small comet lobe is on the left, and the large one on the right. The image has been processed to bring out the comet’s activity, showing majestic jets of material emanating from 67P/C-G. Parts of both lobes are visible, in the lower half of the image, as dark silhouettes against the diffuse glow that envelops the nucleus.

Image above: The original 1024 x 1024 image. Cropped and processed single frame NAVCAM image of Comet 67P/C-G taken on 15 April 2015 from a distance of 170 km to the comet centre. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

The large circular depression on the small lobe is Hatmehit and, to its right, parts of the Bastet region are visible. The large lobe provides an interesting view on the Aker region (the bright-looking portion pointing upwards in this orientation) and on the rough terrains of Khepry (to the right).

For more information about Rosetta mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta

More about...

Rosetta overview: http://www.esa.int/Our_Activities/Space_Science/Rosetta_overview

Rosetta factsheet: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_factsheet

Frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions

In depth:

Rosetta in depth: http://sci.esa.int/rosetta

Images (mentioned), Text, Credit: European Space Agency (ESA).

Greetings, Orbiter.ch

White Dwarf May Have Shredded Passing Planet

NASA - Chandra X-ray Observatory patch.

April 16, 2015

The destruction of a planet may sound like the stuff of science fiction, but a team of astronomers has found evidence that this may have happened in an ancient cluster of stars at the edge of the Milky Way galaxy.

Using several telescopes, including NASA’s Chandra X-ray Observatory, researchers have found evidence that a white dwarf star – the dense core of a star like the Sun that has run out of nuclear fuel – may have ripped apart a planet as it came too close.

Image above: In this Chandra image of ngc6388, researchers have found evidence that a white dwarf star may have ripped apart a planet as it came too close. When a star reaches its white dwarf stage, nearly all of the material from the star is packed inside a radius one hundredth that of the original star. Image Credit: NASA/CXC/IASF Palermo/M.Del Santo et al; NASA/STScI.

How could a white dwarf star, which is only about the size of the Earth, be responsible for such an extreme act? The answer is gravity. When a star reaches its white dwarf stage, nearly all of the material from the star is packed inside a radius one hundredth that of the original star. This means that, for close encounters, the gravitational pull of the star and the associated tides, caused by the difference in gravity’s pull on the near and far side of the planet, are greatly enhanced. For example, the gravity at the surface of a white dwarf is over ten thousand times higher than the gravity at the surface of the Sun.

Researchers used the European Space Agency's INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) to discover a new X-ray source near the center of the globular cluster NGC 6388. Optical observations had hinted that an intermediate-mass black hole with mass equal to several hundred Suns or more resides at the center of NGC 6388. The X-ray detection by INTEGRAL then raised the intriguing possibility that the X-rays were produced by hot gas swirling towards an intermediate-mass black hole.

Image above: X-ray image of NGC 6388. Image Credits: NASA/CXC/IASF Palermo/M.Del Santo et al.

In a follow-up X-ray observation, Chandra’s excellent X-ray vision enabled the astronomers to determine that the X-rays from NGC 6388 were not coming from the putative black hole at the center of the cluster, but instead from a location slightly off to one side. A new composite image shows NGC 6388 with X-rays detected by Chandra in pink and visible light from the Hubble Space Telescope in red, green, and blue, with many of the stars appearing to be orange or white. Overlapping X-ray sources and stars near the center of the cluster also causes the image to appear white.

With the central black hole ruled out as the potential X-ray source, the hunt continued for clues about the  actual source in NGC 6388. The source was monitored with the X-ray telescope on board NASA's Swift Gamma Ray Burst mission for about 200 days after the discovery by INTEGRAL.

The source became dimmer during the period of Swift observations. The rate at which the X-ray brightness dropped agrees with theoretical models of a disruption of a planet by the gravitational tidal forces of a white dwarf. In these models, a planet is first pulled away from its parent star by the gravity of the dense concentration of stars in a globular cluster. When such a planet passes too close to a white dwarf, it can be torn apart by the intense tidal forces of the white dwarf. The planetary debris is then heated and glows in X-rays as it falls onto the white dwarf. The observed amount of X-rays emitted at different energies agrees with expectations for a tidal disruption event.

Image above: Optical image of NGC 6388. Image Credits: NASA/STScI.

The researchers estimate that the destroyed planet would have contained about a third of the mass of Earth, while the white dwarf has about 1.4 times the Sun’s mass.

While the case for the tidal disruption of a planet is not iron-clad, the argument for it was strengthened when astronomers used data from the multiple telescopes to help eliminate other possible explanations for the detected X-rays. For example, the source does not show some of the distinctive features of a binary containing a neutron star, such as pulsations or rapid X-ray bursts. Also, the source is much too faint in radio waves to be part of a binary system with a stellar-mass black hole.

A paper describing these results was published in an October 2014 issue of the Monthly Notices of the Royal Astronomical Society. The first author is Melania Del Santo of the National Institute for Astrophysics (INAF), IASF-Palermo, Italy, and the co-authors are Achille Nucita of the Universitá del Salento in Lecce, Italy; Giuseppe Lodato of the Universitá Degli Studi di Milano in Milan, Italy; Luigi Manni and Francesco De Paolis of the Universitá del Salento in Lecce, Italy; Jay Farihi of University College London in London, UK; Giovanni De Cesare of the National Institute for Astrophysics in IAPS-Rome, Italy and Alberto Segreto of the National Institute for Astrophysics (INAF), IASF-Palermo, Italy.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

For more information about Chandra X-ray Observatory, visit: https://www.nasa.gov/mission_pages/chandra/main/

Images (mentioned), Text, Credits: NASA/Chandra X-ray Center/Megan Watzke/Marshall Space Flight Center/Janet Anderson.

Greetings, Orbiter.ch

Dragon is Berthed to the International Space Station

SpaceX - Falcon 9/Dragon CRS-6 Mission patch.

April 17, 2015

Image above: The SpaceX Dragon space freighter is in the grips of the Canadarm2 robotic arm. Credit: NASA TV.

While the International Space Station was traveling 257 statue miles over the Pacific Ocean just east of Japan, Expedition 43 Flight Engineer Samantha Cristoforetti of the European Space Agency, with the assistance of Expedition 43 Commander Terry Virts of NASA, successfully captured the SpaceX Dragon spacecraft with the station’s robotic arm at 6:55 a.m. EDT.

Dragon arrival at the Space Station and Robotic Arm Capture

Video above: SpaceX Dragon Commercial Cargo Ship Arrives at the International Space Station. Video Credit: NASA TV.

The SpaceX Dragon cargo spacecraft was berthed to the Harmony module of the International Space Station at 9:29 a.m. EDT. The hatch between the newly arrived spacecraft and the Harmony module of the space station is scheduled to be opened Saturday.

The spacecraft is loaded with more than 4,300 pounds of supplies, science experiments, and technology demonstrations, including critical materials to support about 40 of more than 250 science and research investigations during the station's Expeditions 43 and 44.

For more information about the International Space Station (ISS), visit: http://www.nasa.gov/mission_pages/station/main/index.html

For more information about SpaceX and Falcon 9 reusable rocket, visit: http://www.spacex.com/

Image (mentioned), Video (mentioned), Text, Credit: NASA.

Greetings, Orbiter.ch

ALMA Reveals Intense Magnetic Field Close to Supermassive Black Hole

ALMA - Atacama Large Millimeter/submillimeter Array logo.

17 April 2015

Illuminating the mysterious mechanisms at play at the edge of the event horizon

The Atacama Large Millimeter/submillimeter Array (ALMA) has revealed an extremely powerful magnetic field, beyond anything previously detected in the core of a galaxy, very close to the event horizon of a supermassive black hole. This new observation helps astronomers to understand the structure and formation of these massive inhabitants of the centres of galaxies, and the twin high-speed jets of plasma they frequently eject from their poles. The results appear in the 17 April 2015 issue of the journal Science.

Artist’s impression of a supermassive black hole at the centre of a galaxy

Supermassive black holes, often with masses billions of times that of the Sun, are located at the heart of almost all galaxies in the Universe. These black holes can accrete huge amounts of matter in the form of a surrounding disc. While most of this matter is fed into the black hole, some can escape moments before capture and be flung out into space at close to the speed of light as part of a jet of plasma. How this happens is not well understood, although it is thought that strong magnetic fields, acting very close to the event horizon, play a crucial part in this process, helping the matter to escape from the gaping jaws of darkness.

Up to now only weak magnetic fields far from black holes — several light-years away — had been probed [1]. In this study, however, astronomers from Chalmers University of Technology and Onsala Space Observatory in Sweden have now used ALMA to detect signals directly related to a strong magnetic field very close to the event horizon of the supermassive black hole in a distant galaxy named PKS 1830-211. This magnetic field is located precisely at the place where matter is suddenly boosted away from the black hole in the form of a jet.

The team measured the strength of the magnetic field by studying the way in which light was polarised, as it moved away from the black hole.

“Polarisation is an important property of light and is much used in daily life, for example in sun glasses or 3D glasses at the cinema,” says Ivan Marti-Vidal, lead author of this work. “When produced naturally, polarisation can be used to measure magnetic fields, since light changes its polarisation when it travels through a magnetised medium. In this case, the light that we detected with ALMA had been travelling through material very close to the black hole, a place full of highly magnetised plasma.”

Artist’s impression of a supermassive black hole at the centre of a galaxy

The astronomers applied a new analysis technique that they had developed to the ALMA data and found that the direction of polarisation of the radiation coming from the centre of PKS 1830-211 had rotated [2]. These are the shortest wavelengths ever used in this kind of study, which allow the regions very close to the central black hole to be probed [3].

"We have found clear signals of polarisation rotation that are hundreds of times higher than the highest ever found in the Universe," says Sebastien Muller, co-author of the paper. "Our discovery is a giant leap in terms of observing frequency, thanks to the use of ALMA, and in terms of distance to the black hole where the magnetic field has been probed — of the order of only a few light-days from the event horizon. These results, and future studies, will help us understand what is really going on in the immediate vicinity of supermassive black holes.”

Notes:

[1] Much weaker magnetic fields have been detected in the vicinity of the relatively inactive supermassive black hole at the centre of the Milky Way. Recent observations have also revealed weak magnetic fields in the active galaxy NGC 1275, which were detected at millimetre wavelengths.

[2] Magnetic fields introduce Faraday rotation, which makes the polarisation rotate in different ways at different wavelengths. The way in which this rotation depends on the wavelength tells us about the magnetic field in the region.

[3] The ALMA observations were at an effective wavelength of about 0.3 millimetres, earlier investigations were at much longer radio wavelengths. Only light of millimetre wavelengths can escape from the region very close to the black hole, longer wavelength radiation is absorbed.

More information:

This research was presented in a paper entitled “A strong magnetic field in the jet base of a supermassive black hole” to appear in Science on 17 April 2015

The team is composed of I. Martí-Vidal (Onsala Space Observatory and Department of Earth and Space Sciences, Chalmers University of Technology, Sweden), S. Muller (Onsala Space Observatory and Department of Earth and Space Sciences, Chalmers University of Technology, Sweden), W. Vlemmings (Department of Earth and Space Sciences and Onsala Space Observatory, Chalmers University of Technology, Sweden), C. Horellou (Department of Earth and Space Sciences, Chalmers University of Technology, Sweden) and S. Aalto (Department of Earth and Space Sciences, Chalmers University of Technology, Sweden).

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the US National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

Photos of ALMA: http://www.eso.org/public/images/archive/search/?adv=&subject_name=Atacama%20Large%20Millimeter/submillimeter%20Array

The Atacama Large Millimeter/submillimeter Array (ALMA): http://www.eso.org/public/teles-instr/alma/

Image, Video, Text, Credits: ESO/L. Calçada.

Best regards, Orbiter.ch